Thyroid imaging techniques.

Nuclear medicine, ultrasound, CT, and MRI are imaging methods that can be used to evaluate the thyroid gland. All these techniques give structural information about the thyroid gland and show the location and size of thyroid nodules. Nuclear medicine scanning also adds functional information about nodules. In many practices, however, FNA has supplanted imaging methods as the primary method of thyroid nodule evaluation because it is safe, inexpensive, and results in a better selection of patients for operation. Imaging studies are very useful in the setting of recurrent thyroid cancer. Ultrasound is extremely sensitive in the detection of recurrent malignancy in regional cervical lymph nodes and as a guide in performing a biopsy of these nodes. CT is very useful in identifying distant metastases in the chest and abdomen. Nuclear medicine scanning can detect functioning distant metastases when the metastases are from differentiated thyroid cancers. MRI can be used to evaluate the possibility of recurrent thyroid cancer; however, because of its relatively high cost, it is used less frequently than other imaging methods.